remained faithful to John Casimir. They fought in Podlaskie against the Radziwiłłs and took Tykocin. John Casimir himself still in Silesia, issued a universal calling for national resistance against the Swedes, and then on December 18 embarked on a return trip to Poland. The Commonwealth's remaining ally, Crimean Khan Mehmed IV Giray, who had just defeated Khmelnytsky, was offering help and support. The Jasna Góra Monastery of the Pauline Fathers in Częstochowa was under siege for several weeks at the end of 1655. The success of the monastery's defense was of great psychological and spiritual importance for the Poles. The defense efforts at Jasna Góra, a great shrine and fortress with a crew of a few hundred volunteers, were led by Prior Augustyn Kordecki. Before the end of the year, as peasant rescue units approached the site, the Swedish forces were compelled to abandon the siege. The Poles at this stage of the war were becoming increasingly effective militarily. They used the attack against the national shrine as a rallying point; it added a religious dimension and zeal (defense of Catholicism and anti-Protestant) to their struggle. On December 29 the Crown hetmans withdrew their previous support of Charles Gustav and established the Tyszowce military confederation aimed at opposing the Swedish invaders. In January 1656 John Casimir returned from abroad and, impressed by the contributions to the war effort made by Poland's common people, solemnly declared in Lwów his support for relieving the peasantry of unjust obligations. Charles Gustav concentrated on completing the takeover of Prussia. Thorn (Toruń) surrendered without a fight, Marienburg after resisting the siege. Danzig, supported by the Netherlands, remained unconquered. The Swedish king was able to obtain concessions from Frederick William I, the Elector of Brandenburg and Duke of Prussia and vassal of the Commonwealth (in regard to his Prussian rule), who in exchange for Warmia region agreed in Königsberg to become a vassal of Sweden. Charles Gustav then moved south, with the intention of breaking the Polish military opposition. The Poles were still at a disadvantage facing the Swedish army in the open field, and Czarniecki's forces were defeated at the Battle of Gołąb in February 1656. Afterwards the Polish commander successfully applied guerrilla fighting tactics, harassing the enemy while avoiding engagements with the main army. Charles Gustav was soon forced to abandon the siege of Zamość and the planned attack on Lwów. His attempt to